Illusionist David Blaine has been denied entry into the Guinness book of records for his stunts, including one set for Friday in London.
David Blaine will go without food for almost six weeks
US illusionist Blaine - dubbed the modern-day Houdini - asked for his death-defying feats to be recognised.
Compilers rejected his upcoming 44-day stint in a plastic box without food because they would not endorse fasting.
Previous Blaine feats were dismissed, after Guinness World Records said it could not match record titles already held.
Record keeper Stewart Newport said: "We have never encouraged claims for the longest time to voluntarily go without solid food for very clear and obvious reasons.
"If you beat the 'record' and then die is it a successful attempt?"
"We have from a reportage standpoint noted in past books various political, medical and criminal 'hunger strikes' - and all were for durations far in excess of 44 days," Mr Newport added.
On Friday, Blaine will climb into a small Perspex box, suspended from a crane above the River Thames, close to Tower Bridge.
He will then attempt to stay without food for more than six weeks, with no communication or distractions. His only nourishment will be from a tube feeding him water.
The stunt will be televised on Channel 4 and Sky One - including live coverage throughout the entire 44 days on Sky.
The box in which he aims to spend 44 days measures just 7ft by 7ft by 3 ft (2.1m by 2.1m by 0.9m).
It will contain trickling water and a tube for him to urinate - by which doctors will be able to assess his health.
Blaine said he weighed 205 lb (93 kg), having begun an added glucose diet, and expected to lose about 45 lb (20 kg) during more than six weeks without food.
Record-keepers at Guinness also rejected Blaine's most recent stunt on the grounds that it could not surpass records previously set.
Vernon Kruger stayed in a barrel in South Africa - about an eighth the size of Blaine's box - for 67 days in 1997, they said.
In addition, the longest hunger strike ended in 1973 after 385 days when Dennis Galer Goodwin protested his innocence in Wakefield Prison, West Yorkshire, of a rape charge. He was fed orally, using a tube.
Blaine's previous stunts, including encasing himself in six tons of ice for three days and being buried alive, were also rejected for similar reasons.
Sky One will show him going into the box live on Friday evening, with Channel 4 showing the footage three days later.
His exit is due to be shown live on Sky One on 19 October and on Channel 4 the following day.